JPS62998B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a method for oxidizing para-tertiary butyltoluene. Specifically, the present invention relates to a method for producing para-tertiary butyl benzyl acetate, para-tertiary butyl benzylidene diacetate, and para-tertiary butyl benzaldehyde. More specifically, para 3.
Para-tertiary butyl benzyl acetate, para-tertiary butyl benzylidene diacetate, and para-tertiary butyl benzylidene diacetate, which are characterized by electrolytically oxidizing butyl toluene.
Concerning the production of class butylbenzaldehyde. Generally, oxidation of the benzyl position of an alkyl group substituted on the benzene nucleus is carried out by chemical oxidation using an oxidizing agent or autooxidation using a catalyst [Proceedings of the Chemical Society of Japan Autumn Annual Meeting P596 (1978), ANBashkirvet al, Ger.
Offen.1912078 (1970), Fr 2036499 (1970)] or electrolytic oxidation method, these methods can produce the corresponding benzyl alcohol, benzaldehyde,
Alternatively, it is known to be converted into benzoic acid derivatives. However, in the first two cases, for example, the oxidizing agent is required to be stoichiometric or higher. Catalysts are also relatively expensive and generally have poor selectivity. On the other hand, the latter electrolytic method involves the active species generated on the electrode surface directly participating in the reaction, so it has the potential to be completed as an economical method. However, since a nucleophilic substitution reaction to aromatic nuclei also occurs, disadvantages such as poor product selectivity and low conversion rate have been pointed out. For example, SD Ross et al. [J.Org.Chem, 35 , 781
(1970)] electrolyzed toluene in acetic acid with tetraethylammonium paratoluene sulfonate as a supporting salt using a carbon electrode, and produced a mixture of bibenzyl, benzyl acetate, benzaldehyde, acetoxytoluene, etc. It has gained. The conversion rate at this time was 14.4%. Also, Shono et al. [J.Org.Chem., 35 , 4157
(1970)] electrolyzed paracymene in methanol using tetraethylammonium paratoluenesulfonate as a supporting salt using a carbon electrode, and the products were 1-isopropyl-4-methoxymethylbenzene, paraisopropenyltoluene, para- (2-methoxyisopropyl)toluene each
The yields were 14%, 10%, and 19%. Furthermore, A. Nilsson et al. [J.Chem.Soc.Parkin I,
708 (1978)] electrolyzed paraxylene in methanol, using lithium tetrafluoroborate as a supporting salt and sodium methoxide as a base, using a carbon electrode as an anode and a tungsten electrode as a cathode, to generate the product. Fractionated to produce 57% paramethylbenzaldehyde dimethyl acetal as the main product
It has been obtained with a yield of . These methods support a wide variety of products and still have problems such as poor conversion rates. By the way, as mentioned above, the conditions used for electrolytic oxidation of alkylbenzene, namely, quaternary ammonium salt in acetic acid [SD Ross et al, J.Org.Chem.
35 , 781 (1970)] or an acetate salt such as sodium acetate [L.Eberson, J.Am.Chem., Soc., 88
1686 (1966)] as a supporting electrolyte, para-tertiary butyltoluene was electrolyzed in acetic acid using a platinum or carbon electrode, and sodium acetate or tetraethylammonium para-toluene sulfonate was supported using a carbon electrode. When electrolyzed as an electrolyte, many by-products were obtained in addition to the desired para-tertiary butylbenzyl acetate, resulting in poor selectivity and poor conversion. As described above, under the previously reported electrolytic conditions, the conversion rate, products, and selectivity are low.
This method cannot be used as an industrial synthesis technique for oxidizing the side chain of para-tertiary butyltoluene. In recent years, L.Eberson et al. [Acta Chem.Scand,
B29, 617, (1975)] developed an electrolysis device incorporating a capillary gear capsule that was capable of large-scale electrolytic synthesis on a laboratory scale, and using this,
Electrolysis of para-tertiary butyltoluene was carried out in acetic acid using tetrabutylammonium tetrafluoroborate (Bn ₄ NBF ₄ ) as a supporting salt at 20 A and 60 V. It has been reported that butylbenzyl acetate can be obtained. The present inventors achieved this without using an expensive supporting salt such as tetrabutylammonium fluoroborate.
As a result of searching for a new electrolytic solution system for selectively and stepwise electrolytic oxidation of the methyl group of para-tertiary butyltoluene, we found that either the desired two-electron oxidation product or four-electron acid product was produced. The present invention has been completed by discovering electrolytic reaction conditions that produce a high yield of 73 to 81%. The present invention is characterized by an electrolytic solution system for selectively electrolytically synthesizing para-tertiary butyl benzyl acetate, which is a two-electron oxidation product, and para-tertiary butyl benzylidene diacetate, which is a four-electron oxidation product, and its hydrolysis. The electrolytic solution system for selectively electrolytically synthesizing the product, para-tertiary butylbenzaldehyde, has the same solvent, supporting salt, additives, etc. that constitute the electrolysis, and only the electrolytic conditions such as current density and electric current are the same. Either the two-electron oxidation product or the four-electron oxidation product described above can be advantageously produced by simply changing the amount, if necessary, by slightly changing the amount of support and additives in order to change these physical quantities. This is an innovative manufacturing method that allows for To explain in detail the relationship between electrolytic conditions and product selectivity according to the present invention, when para-tertiary butyltoluene is electrolyzed in an acetic acid solvent and sodium acetate, lithium perchlorate, etc. are used as a supporting salt, In addition to para-tertiary butyl acetate, a considerable amount of nuclear acetoxylated products, dimers, and other resinous substances are produced as by-products. However, when ammonium tosylate is used as a supporting salt, only oxidized products of side chain methyl groups are obtained.
However, this electrolytic system has a conversion rate of about 30-40% and cannot be used for synthetic reactions. After examining the electrode and electrolyte compositions to improve conversion rate and selectivity, we found that carbon electrodes and acetic acid
The combination of tertiary butyl alcohol (10:1) improved the conversion to 50-65% and also increased the selectivity. Furthermore, when electrolysis was attempted with various additives coexisting in the electrolytic system, acetates, sulfates, halogen salts, etc. of metals such as copper, lead, iron, cobalt, and cerium coexisted at 5 to 20 wt% relative to the supporting salt. It was found that the conversion rate and selectivity were both significantly improved, and side chain oxides could be obtained with a yield of 74 to 89%. It was also found that two-electron oxidation products were produced with a yield of over 70%. In this way, we used a carbon-based electrode, a quaternary ammonium salt of para-toluenesulfonic acid as a supporting salt in an acetic acid-tertiary butyl alcohol mixed solvent system, and an electrolytic solution in which additives such as copper acetate were coexisting. ,
It has been found that the desired para-tertiary butyl benzyl acetate can be synthesized advantageously by electrolyzing with the addition of para-tertiary butyl meruene, but one of the characteristics of this electrolytic method is that the electrolytic reaction in such an electrolytic solution system has a low current density. It is possible to control product selectivity using the amount of electricity and the amount of electricity as clues. Another feature is that in such an electrolytic solution system, two-electron oxidation reactions and four-electron oxidation reactions can be controlled using current density and quantity of electricity as cues. In other words, in two-electron electrolytic oxidation, there is some variation depending on the shape of the carbon electrode used.
When electrolysis is carried out under the conditions of applying electricity of 6 F/mol or less at a current density of 10 mA/cm ² or less, 4-electron oxidation products are produced as the main product at 0 to 10%, and when both are combined, side chains Oxidation products form 70-80%.
In order to generate a 4-electron oxidation product, 10~
Electricity of 6~ at current density in the range of 200mA/ ^cm2
When electricity is applied in the range of 40 F/mol, the four-electron oxidation products para-tertiary butyl benzylidene diacetate and para-tertiary butyl benzaldehyde are produced in a combined yield of 59 to 71%, and the two-electron oxidation products are It is possible to control the product by 3-10%. In this way, the present invention has investigated electrolytic conditions for selectively electrolytically synthesizing industrially important two-electron oxidation products and four-electron oxidation products, respectively, by electrolytic acetoxylation of para-tertiary butyltoluene. The solvent, supporting salt, additives, current density, quantity of electricity, etc. used in the present invention are not limited to the representative examples illustrated above. Furthermore, there are various combinations of various electrolytic factors related to the present invention, and it is possible to arbitrarily select desirable and excellent electrolytic conditions. Preferred electrolytic solvents, supporting salts, additives, electrolytic conditions, etc. are detailed below. Metal salts or metal oxides as additives used in the method of the present invention include acetates such as copper acetate, cobalt acetate, manganese acetate, lead acetate, iron acetate, cerium acetate; copper sulfate, cobalt sulfate, sulfuric acid. Sulfates such as iron, manganese sulfate, lead sulfate; copper nitrate,
Nitrates such as cobalt nitrate, manganese nitrate, lithium nitrate, sodium nitrate, potassium nitrate, iron nitrate, lead nitrate; Chlorides such as copper chloride, cobalt chloride, iron chloride, manganese chloride, lead chloride; Copper bromide, cobalt bromide, Examples include bromides such as iron bromide, manganese bromide, and lead bromide, and oxides such as copper oxide, cobalt oxide, iron oxide, manganese dioxide, and lead oxide.
Among these, it is preferable to use copper salts. The amount of metal salt or oxide used in this reaction is usually 0.1 to 0.1 to para-tertiary butyltoluene.
100wt%, preferably in the range of 1 to 50wt%. Even if these metal salts and oxides are difficult to dissolve in the present electrolytic system, sufficient effects can be expected even if they are used as a heterogeneous system. The solvent used in the method of the present invention is acetic acid or a mixed solvent containing acetic acid as the main solvent. That is, more favorable results are often obtained when an appropriate amount of co-solvent is added to acetic acid than when using an acetic acid single solvent system. Here, the cosolvent used with acetic acid is:
For example, isopropanol, cyclohexanol,
Secondary or tertiary alcohols such as tertiary butyl alcohol and tertiary amyl alcohol; Nitriles such as acetonitrile, propionitrile, butyronitrile; Aprotons such as ethyl acetate, (or methyl), acetone, methyl ethyl ketone, ether, and tetrahydrofuran solvents, etc. can be used.
Here, it is preferable to use secondary or tertiary alcohols. The amount of these alcohols used is 1 to 100% by volume relative to acetic acid.
%, preferably in the range of 50%. The amount of acetic acid or a mixed solvent containing acetic acid as the main solvent used in this reaction is 1 to 1000 times, preferably 1 to 500 times, by weight relative to para-tertiary butyltoluene. Supporting electrolytes used in this electrolytic reaction include, for example, tetramethylammonium para-toluenesulfonic acid, tetraethylammonium para-toluenesulfonic acid, tetrabutylammonium para-toluenesulfonic acid, tetramethylammonium perchlorate, tetraethylammonium perchlorate, and perchloric acid. Quaternary ammonium salts such as tetrabutylammonium; Amines such as lower alkyl-substituted primary, secondary, and tertiary amines (alkyl groups include methyl, ethyl, propyl, and butyl groups), pyrrolidine, and pyridine; Perchlorine of metals Acid salts (alkali metals such as lithium, sodium, potassium, etc.)
Metal nitrates (metals include alkali metals such as lithium, sodium, potassium, and copper, cobalt, iron, lead, etc.); Alkali metal acetates (metals include lithium, sodium, potassium, etc.);
Inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid and their quaternary ammonium salts (alkyl groups include methyl,
(ethyl, propyl, butyl groups); more preferably quaternary ammonium salts, such as tetraethylammonium para-toluenesulfonic acid, give good results. The amount of these supporting salts to be used is 0.1 to 50 times, preferably 0.2 to 20 times, the weight of para-tertiary butyltoluene. For the electrolytic reaction of the present invention, ordinary electrodes for electrolysis, ie, electrodes made of materials such as platinum, carbon, nickel, lead, etc., can be used, but carbon electrodes are preferably used. Also, the temperature during electrolytic reaction is usually 5 to 100℃.
°C, preferably in the range of 15 to 50 °C. As the electrolytic reaction method, constant potential electrolysis and constant voltage electrolysis are also possible, but a simpler method of current density regulation can be adopted. Direct current or alternating current electrolysis can be used for electrolysis. For example, a method in which the direction of current is switched every 0.5 to 20 minutes can give preferable results. The electrolytic reaction according to the present invention does not require separate anodes and cathodes in the electrolytic reaction tank, so it does not require a diaphragm, and can be operated in a single electrolytic tank, whether it is a batch type or a continuous type electrolytic tank. , vertical type,
Either type of electrolytic cell, stacked type or fluidized type, may be used. Para-tertiary butyl benzyl acetate produced by the method of the present invention can be combined with appropriate synthesis processes to produce industrially used para-tertiary butyl benzaldehyde. Furthermore, para-tertiary butyl benzylidene diacetate produced according to the present invention can be easily converted to para-tertiary butyl benzaldehyde by hydrolysis. The method of the present invention will be specifically explained below using Examples. Example 1 In a test tube with a branch as shown in Figure 1, 1.0 g (6.75 mmol) of para-tertiary butyltoluene, 0.9 g (3.20 mmol) of tetraethylammonium para-toluenesulfonic acid as a supporting electrolyte, and 0.1 g of copper acetate as an additive. Weigh out. more acetic acid
Add 7.0 ml and 0.7 ml of tertiary butyl alcohol to make a homogeneous solution. A rotor, a thermometer, and carbon electrodes (1.5 x 3 cm ² ) are attached to this. Then, at room temperature, while switching the anode and cathode alternately, the current density was 50 mA/1.5 x 3 cm ² and the terminal voltage was 3~
7 volt constant current electrolysis for 21.72 hours (6F/mol)
conduct. After the reaction was completed, most of the acetic acid was distilled off under reduced pressure, then normal hexane was added, washed with saturated aqueous sodium bicarbonate solution 2 to 3 times, and washed with saturated brine 2 to 3 times.
Wash twice. Then, it is dried over anhydrous sodium sulfate and the solvent is distilled off under reduced pressure. The crude product is purified using a silica gel column to obtain 1.076 g (yield 77.3%) of para-tertiary butyl benzyl acetate. The gas chromatogram purity of this item is 99.5%
It is. Examples 2 to 8 and Reference Examples 1 to 3 The same procedure as in Example 1 was carried out with different additives and supporting electrolytes, and the results shown in Table 1 were obtained. We also show the results obtained by changing the solvent and supporting electrolyte without adding any additives. Example 9 Weigh out 0.1 g (0.67 mmol) of para-tertiary butyltoluene, 1.0 g (3.56 mmol) of tetraethylammonium para-toluenesulfonic acid as a supporting electrolyte, and 0.1 g of copper acetate. Furthermore, add 7.0 ml of acetic acid and 0.7 ml of tertiary butyl alcohol to make a homogeneous solution. This raw material solution was subjected to constant current electrolysis at a current density of 100 mA/1.5 x 3 ^cm2 and a terminal voltage of 5 to 11 V for 5.58 hours (30/3 cm2) in the same manner as in Example 1.
After purification, para-tertiary butyl benzyl acetate, para-tertiary butyl benzaldehyde,
para-tertiary butyl benzylidene diacetate, respectively
Obtained with yields of 5.5%, 23.7%, and 46.9%. Examples 10 to 15 Table 2 shows the results obtained by performing the same operation as in Example 9 by changing the current density and amount of electricity, and the results obtained without adding tertiary butanol.

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【table】 [Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention. 1... Thermometer, 2... Carbon electrode, 3... Stirrer.

Claims (1)

[Claims] 1. At least one selected from para-tertiary butyl benzyl acetate, para-tertiary butyl benzylidene diacetate, or para-tertiary butyl benzaldehyde is obtained by electrolytically oxidizing para-tertiary butyl toluene in a solvent containing acetic acid in the presence of a supporting salt. 1. A method for oxidizing para-tertiary butyltoluene, which is carried out in the presence of a salt or oxide of a metal selected from copper, cobalt, manganese, lead, iron and cerium.